It is generally known that hyaluronic acid and/or a hyaluronic acid compound are excellent in moisturizing power to skin and has effects of beautifying the skin by providing the skin with elasticity, moisture or firmness. Various cosmetic solutions have developed using hyaluronic acid and/a hyaluronic acid compound.
Conventionally, as a cosmetic solution containing hyaluronic acid and/or a hyaluronic acid compound, one obtained by using a sodium hyaluronate as a hyaluronic acid compound, mixing about 0.1% of the sodium hyaluronate with water, and further mixing a preservative such as phenoxy ethanol or paraben has been widely used.
In this cosmetic solution, since a preservative is contained, it irritates the skin. Therefore, this solution has defects that when it is in contact with the skin for a long period of time, it may induce systematic toxicity by percutaneous absorption, or the like.
In order to solve the problem, a technology disclosed in JP-A-2006-182750 (Patent Document 1) has conventionally been known. This is a product obtained by freeze-drying an aqueous solution comprising sodium hyaluronate, an ascorbic acid derivative and collagen. The freeze-dried powder is put in a container, and after substituting the inside of the container with a nitrogen gas, the container is sealed by a rubber stopper to eliminate the presence of oxygen, whereby the powder is preserved such that no water content is absorbed. When used, this freeze-dried powder is re-dissolved in water or in a cosmetic solution.